Masking of photographic color film



March 23, 1954 R W. CONANT MASKING OF' PHOTOGRAPHIC COLOR FILM Filed Sept. l2, 1952 .11... 1.1.4.1....I'an'q'unp'l azz/f ,45,0567

Patented Mar. 23, 1954 UNITED STATES `PATENT OFFICE 2,673,150 MASKING F PHOTOGRAPHIC COLORFILM Russell W. Conant, Los Angeles, Calif., assignor to Technicolor Motion Picture Corporation, Hollywood, Calif., a corporation of Maine Application September 12, 1952, Serial No. 309,301 8 Claims. (Cl. 95-2) 1 The present invention relates to color photogas a whole certain disadvantages due among other raphy and more particularly to a method of corfactors to the necessity of using separate auxilrecting color film for color falsiication, and to iary records with the attendant problemsof procolor iilm containing corrective mask records. cessing and registration. These disadvantages The present application is a continuation in part .5 are particularly felt in the field of color photogof my copending application Serial No. 15,863, raphy with so-called integral packs or multifiled March 19,1948, now abandoned. layer photographic material also` referred to as Photographic color records which consist of monopacks. Since conventional masking procsuperimposed records in subtractive coloring matesses with detached auxiliary records introduce ter are subject to detrimental eiects of imperi.) factors which multi-layer material otherwise infect properties of components involved in making herently avoids, it has been proposed to provide the records, particularly defective transmission integral packs with mask records in separate 0f the subtractive coloring matters. These colorlayers which in themselves are not required for ing matters, in most instances dyes, instead of the formation of any part of the original color absorbing only the `spectral range of the color i5 image. While such integral mask layers elimiaspect which they record, absorb in addition specnate the registering problem, they introduce other tral ranges which are recorded in other dyes of disadvantages into the already complex structhe same picture. For example, the cyan (red tures and processing techniques of multi-layer absorbing) dye which is used for reproducing color films.

the red filter aspects, absorbs in addition to red 2o It is one of the principal objects of the present light also some light in the green and blue ranges, invention to provide a masking technique for lthus falsifying the nal record wherever it conmulti-layer photographic material which has all tains these ranges. These and other deiiciencies, the advantages of the conventional masking techfor example those due to imperfect properties of niques while avoiding unattached auxiliary reclters and sensitivity characteristics of emulsions, ords as well as integral or attached emulsion can be partially corrected by means oi so-called layers specically provided for masking. Other masks. These masks are auxiliary records of apobjects of the invention are to provide a multipropriate photographic sign and gradation, delayer color record which includes a masking recpending upon the `peculiarities of the defects to ord without requiring more emulsion layers than be corrected in each instance, and are used for those-for the main records, to provide a technique printing in optical superimposition with main of partially removing the silver of a multi-layer records to be corrected. Thus, in the above menphotographic film which technique is particulartioned example, a negative low gradation mask ly suitable for purposes of the present invention, would be made from the red aspect positive (in and to provide process components and photocyan dye), and used for printing from the blue graphic materials which are suitable for purposes aspect positive (in yellow dye) and the green of the present invention of masking multi-layer aspect positive (in magenta dye), so that a ceror mono-pack iilm material of the conventional tain amount of the blue and green light absorbtype. ing effect of the cyan dye is subtracted respec- In one of its aspects, the invention achieves tively from the blue and green aspect records, 4U these objects by recording a color original in the namely that much as is instead supplied by the form of at least two registeringly superimposed improper blue and green light absorptions of the main records in coloring matter contained in cyan dye. Thus, the `unwanted blue and green emulsion layers which also contain metallic sillight absorptions of the cyan dye of the red aspect Ver, and thereupon substantially removing the positive are cancelled out. entire silver in one of these emulsions and sub- Theoretically, a maximum color correction can stantially removing the silver co-extensive with be carried out with the aid of six auxiliary recthe main record in the `other emulsion. In anords, two for each main record, with gradation other aspect, the invention makes use of the cirproperties dependent upon the deciencies to be cumstance that the silver particles co-extensive corrected. For most practical purposes, a single 59 with an original dye record diiier from those asmask, or if particularly effective correction is desociated with the rst or negative stage of develsired, two masks have been found to be sufcient. opment in number or character such as to make Nevertheless, masking with auxiliary records them diierently susceptible to chemical agents which are derived `by exposure from the main suitable to affect these silver particles so that, records introduce 'into the photographic process `55 for example, a bleaching agent can be applied which substantially aifects primarily the silver co-extensive with a record obtained by conventional reversal technique leaving a silver record of photographic sign opposite to that of the reversal record. In accordance with a more specific feature of the invention, a negative mask derived from the red filter aspect is obtained by completely bleaching the silver in the outer and intermedaite, or blue and green recording layers of a multi-layer iilm and in obtaining a negative silver record in the lowermost layer containing the cyan positive record, by differentially bleaching the more iinely divided silver in that lowermost record which fine grain silver generally speaking photographically corresponds to or is coextensive with the positive record, so that the more coarse grained silver, complementary thereto, remains and constitutes the negative mask record whose gamma can be controlled in some degree by the aforesaid bleaching technique. According to a further aspect or the invention, two masks, for example ior correcting improper absorption of the cyan as well as yellow dyes is provided by proceeding according to the above char- Y acterized technique and in addition redeveloping a negative image of comparatively low gamma near the outer surface of the uppermost or blue recording layer of the multi-layer nlm material.

These and other objects, aspects and features will appear from the following description of two typical practical embodiments illustrating the novel characteristics of my invention. This description refers to a drawing in which Fig. l is a now diagram illustrating a masking process which corrects deficiencies of the cyan printing dye;

Fig. 2 is a diagram illustrating the dineren-tial bleach eifect; and

Fig. 3 is a similar 'flow diagram illustrating correction according to the invention, for deficiencies oi the cyan as well as yellow dyes of a multi-layer color lm.

1n the figures, F indicates a support, such as nitrate or acetate cellulose lm material, which support carries three emulsion layers b, g, 1', in conventional manner sensitized and otherwise arranged to record the blue, green, and red color aspects ol an original. This multi-layer sensitive material may incorporate additional layers, such as antihalation and filter layers, which are not shown in order to simplify the drawing. The commercially available nlm material Eastman Kodak type 5267 was found suitable for the purpose, but it should be understood that the invention is applicable to other film material of this general type.

After exposure to an original, which may be a colored scene or a record in colors, the film is subjected to conventional reversal development. This can comprise the steps of rst developing all originally exposed silver halide particles, thereupon in succession selectively exposing, with colored light, the originally unexposed film layer portions of corresponding sensitivity and developing them successively in color developing solutions. An alternative technique employing film material of the type which contains in each emulsion layer a color former appropriate for producing with a suitable single developer solution a dye record appropriate for the respective layer can comprise the steps of subjecting the entire film to uniform initial development and reversal exposure, and thereupon simultaneous development of three color positives. In either case, a multi-layer nlm record is obtained which, Aas

illustrated at the second stage of the iiow diagram according to Fig. l, includes yellow, magenta, and cyan positive records, the film also containing at this stage silver particles s throughout each emulsion. According to conventional procedure this silver is bleached out in its entirety to pr duce emulsion layers which contain only the dye records.

It will be understood that the various records herein referred to are not actually strictly separated or associated with one or the other surface of an emulsion layer, as sho-wn in the drawing for the sake of clarity. Also, wherever the present specification refers to photographically corresponding or coextensive silver and dye records, this correspondence is understood to be of the type which results for example from color development of the type wherein a silver record is produced together with a dye reocrd.

In accordance with the invention, the silver is not entirely but only partially removed in a manner peculiar to the `present invention, as follows.

This diiferential removal of the silver is made possible by the fact that the residual silver of a partially bleached multi-layer record is itself a record and has a definite relation to the original record. It is common knowledge that the silver record corresponding to or photographically coextensive with the Yfinal positive dye record differs from the negative silver record; one dierence is that its grain distribution is statistically different as compared. to that of the negative record produced during the first or original development.

VThe reversal record has more fine grain than the original record; in other words the grain size coordinate of the statistical grain distribution curve of the original record is for a given grain number per unit, greater than the size coordinate of the reversal record.

A given bleaching agent will in a given time interval totally consume grain below a certain size, While coarser grain will be diminished in size, yet remain to form a visible record. Hence, given two records of the above different grain size distribution, the record which is generally finer will be reduced in greater proportion than that of the statistically coarser grain deposit. Therefore two records of diiferent grain distribution such as the above described original and or reversal developed records, can be differentiated in a bleaching procedure which at any given instance has removed more density from the finer grained record as compared to the coarser record. Hence by interrupting the bleach at a selected stage, a desired relation between the records can be accomplished which is useful for the present purpose, furnishing a residual negative record and a positive record of smaller contrast, the resultant of both being the desired masking record having at least approximately predeterminably gamma in the proper, namely negative sense, and in the range useful for color correction masking. This selective effect is illustrated in Fig. 2 which shows the distribution curves of original and reversal records and indicates the differentiating eifect of a bleach which has acted long enough to eliminate all grain up to a certain size.

f the mask is to be formed in the lowermost or intermediate layer it is desirable to use a bleaching technique which accomplishes the desired distribution, namely essentially no silver in the upper layers or layer and silver remaining in the layer therebelow sufficient for providing the mask record in the above manner. This kthe lower layer is subjected to a result. namely essentially `complete removal of silver from the upper layers while the `above control takes place in the layer therebelow, can be accomplished 'with one and the `same bleach, but it is 'easier to bleach `the upper layers essentially completely with a comparatively strong 4acting 'bleach which stopped when it gion between upper and lower layers, whereupon more prolonged and hence better vcontrollable bleach to attain the masking record inthe above outlined inanner.

Accordingly, and referred again to Fig. 1, the lm which now carries yellow, magenta and cyan `dye images, indicated at y, m and c of Fig. 1, and in addition thereto silver throughout the three emulsions, as indicated at s of Fig. 1, is rst subjected to a preliminary Aconcentrated `-bleach, for example according to the following technique.

Soak in water for live minutes; bleach for 45 seconds in a solution containing 47 grams per litre of sodium dipotassium vierricyanide :(KzNaFelCNls) and grams per litre of potassium bromide (KBr); stop the bleach by soakfor one minute in a solution of 20 grams NaHSOs per litre of solution; land rinse in water for seconds.

'This bleaching bath removes the silver from layers b and g, but leaves a substantial portion of the silver inthe lowermost layer r.

A selective bleach, more dilute in accordance with the above principle, is now applied as follows.

Bleach for one minute in a'solution containing C 23 grains per vlitre of K2NaFe(CN)e, and 10 grams vper litre of KBr; stop this bleach by soaking the lm material for one minute in a solution of for seven minutes in a solution of 250 grams per litre oi liking salt, Na2S2'O3-5H2`O; wash in water for 10 minutes; blow off the excess water; and dry.

can be obtained by conventional control of the 'above indicated bleaching technique which is enhanced by the `prolonged time available if the dilute bleach is used, although it is understood that in instances not requiring particularly exact control, the more concentrated bleach which permits only more restricted control possibilities can be used throughout.

.A set of `mask corrected `separation negatives can now 'be made from the original containing the silver mask record sn, by consecutively printing with blue, green and red light. During the printings with blue and green light the mask cancels the unwanted blue and respectively, of the cyan dye to the extent represented by the gamma of the mask. Better blue -and .green separation negatives result. Fig. 1 ,Shows this printing step for the blue aspect sepe "'ara'tion negative B, indicating absorption @of the blue printing light by Lthe 'yellow dye lof the vblue aspect 'positive yand by `the inask lrecord The mask fs'n .has no corrective `effect with Vregard to the red aspect printing, but freoluce'sthe printing contrast of the red aspect `separaticm negative, which icontrast can be restored `by proper fchoice `or developing 1time lin conventional manner. l

Ii it is desired to correct also lfor `the 'im-proper absorption of the yellow dye in 'the green spectral range, #a mask has to fbeintroduced which is fderivedirom the blue Jlter aspect, `according to the invention. This record is produced the outer layer 4by partly redeveloping the silver 's'alt obtained by bleaching `the outer layer.

masking technique 'is indicated lin above mentioned red 'aspect mask record en, `de- `noted am' in Fig. 3.

20 gram per litre solutionof sodium bisulph-ite I"(NaHSOaD. Apply now the more diluted bleach described ilabove, namely"23 grams per litre of KzNaFeCCNls and l 'grams `of KBr, stop this bleach `with the above NaHSOa solution, wash in water `for 1 minute; redevelop for 30 seconds in an MQ ydeveloper of Aconventional composition; wash in wa-ter for 3 minutes; iii: in hypo solution for 7 minutes; and wash in water for 10 minutes. The temperature 'of all liquid baths should be about 70 F.

The above described `procedure results with 'nlm material of the above indicated type, in 'a Iblue aspect masking record s'nb having a `gamma.

scribed above with reference to Fig. l.

the printing with blue light, the b-lue record, dened by the yellow dye record y together with the blue aspect mask snb, is corby separation negative developing During the printing with green light `of the magenta dye record m, the -r'ed aspect mask sm and the blue aspect snr has no masking eiect but causes considerable reduction of contrast which can be corrected by development control. The blue aspect mask snb tends to eiiect, during this red light printing, cancellation of the unwanted absorption of the yellow dye in the red range. rI'his latter eiect will most likely be an overcorrection since the absorption of the yellow dye in the red range is quite slight. However, since the gamma of the blue aspect mask sub is relatively low, this overcorrection is negligible.

As indicated above, the records can be so controlled by conventional methods that the presence of two masks during all three printings is either benecial or unobjectionable. Ii desired, mask records can be bleached out after making the print or prints for which they are needed.

It will be evident that the invention does not necessarily have to be carried out with the purpose of obtaining, as nal results, three separation negatives, but can be used for making prints on multi-layer material, whereby the colored light used for the corrective printing will only affect the layer which is sensitive thereto, in accordance with the particular construction of the multi-layer copying material.

It will further be observed that the invention is not limited to the particular spectral ranges discussed above by way of example, but that it can be utilized for correcting colored records in any spectral ranges suitable for various purposes.

While the above described technique proved satisfactory for commercially available multilayer iilm, variations in the characteristics of the emulsion layers may require changes in treatment times or concentrations which are to be determined by the customary production tests.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. In the art of correcting color photographs for deciencies of color rendition, the method comprising the steps of recording a color original in film having at least two superimposed silver halide layers; developing the exposed portions in black and white developer; reversal developing the residual records in color forming developer, thereby producing negative comparatively coarse grain silver records and positive records co-eX- tensive with the color developed records, oi comparatively 'finer grain, and susceptible to removal by a seelctive bleaching agent which has less effect on said coarse grain records than on said rlne grain records; removing substantially the entire silver in one of said layers; and treating the other layer with said selective bleaching agent for a time suicient to remove a substantial portion of the silver of said ne grain positive record but to leave a corrective silver mask consisting predominantly of coarser grain and being oi lower gamma than said color developed records.

2. The method according to claim 1 wherein said ne grain silver in said other layer is removed by time limited treatment in a solution containing alkali metal ferricyanide and alkali metal halide.

3. The method according to claim l wherein said silver in said one of said layers is essentially removed with a comparatively bleaching agent and said silver in said other layer gammas oi the various concentrated is bleached with a ing agent.

4.. The method according to claim 3 wherein said bleaching agents are compartively concentrated and dilute solutions, respectively, oi essentially the Same agen 5. The method according to claim 4 wherein said bleaching agent is a solution containing alkali metal ferricyanide and alkali metal halide.

6. In the art of correcting color photographs for deiiciences of cyan dyes, the method comprising the steps of recording blue, green and red aspects of a color original in film having three superimposed silver halide layers for the respective aspects; developing the exposed portions in black and white developer; reversal developing the residual records in yellow, magenta and cyan color forming developers, respectively, thereby producing negative comparatively coarse grain silver records and positive records co-extensive with the color developed records, oi comparatively finer grain, and susceptible to removal by a selective bleaching agent which has less effect on said coarse grain records than on said finer grain records, removing substantially the entire silver in said yellow and magenta developed layers; and treating the cyan developed layer with said selective bleaching agent for a time suiiicient to remove a substantial portion of the silver of said rine grain positive record but to leave a corrective silver mask consisting predominantly of coarser grain and being of lower gamma than said color developed records.

7. In the art of correcting color photographs for deficiencies of color rendition, the method comprising the steps of recording a color originail in nlm having three superimposed silver halide layers; developing the exposed portions in black and white developer; reversal developing the residual records in color forming developer, thereby producing negative comparatively coarse grain silver records and positive records co-eX- tensive with the color developed records, of comparatively finer grain, and susceptible to removal by a selective bleaching agent which has less effect on said coarse grain records than on said finer grain records; converting substantially the entire silver in two of said layers into a redevelopable optically substantially ineffective compound; treating the third layer with said selective bleaching agent for a time sufficient to remove a substantial portion of the silver of said fine grain positive record but to leave a corrective silver mask consisting predominantly of coarser grain and being of lower gamma than said color developed records; and redeveloping in one of said two layers a part of said compound which corresponds cssentially to said coarse grain record, to an extent suirlcient to form a corrective silver mask of lower gamma than said color developed records.

8. In the art of correcting color photographs for deciencies of color rendition, the method comprising the steps of recording blue, green and red aspects of a color original in film having three superimposed silver halide layers; developing the exposed portions in black and white developer; reversal developing the residual records in yellow, magenta and cyan color forming developer, thereby producing negative comparatively coarse grain silver records and positive records co-extensive with the color developed records, of comparatively finer grain, and susceptible to removal by a selective bleaching agent which has less effect on said coarse grain records than on said comparatively dilute bleachner grain records; converting substantially the entire silver in the yellow and magenta, developed layers into a redevelopable optically substantially ineffective compound; treating the cyan developed layer with said selective bleaching agent for a time sulicient to remove a substantial portion of the silver of said fine grain positive record but to leave a corrective silver mask consisting predominantly of coarse grain and being of lower gamma than said color developed records; and redeveloping in said yellow developed layer a part of said compound which corresponds essentially to said coarse grain record, to an extent sufficient to form a corrective silver mask of lower gamma than said color developed records.

RUSSELL W. CONANT.

References Cited in the lle of this patent UNITED STATES PATENTS Number Number Name Date Evans et al Mar. 12, 1940 Evans June 4, 1940 Evans et al Feb. 11, 1941 Hanson Dec. 7, 1943 Morris Jan. 4, 1944 FOREIGN u PATENTS Country Date Great Britain Sept. 21, 1939 

1. IN THE ART OF CORRECTING COLOR PHOTOGRAPHS FOR DEFICIENCIES OF COLOR RENDITION, THE METHOD COMPRISING THE STEPS OF RECORDING A COLOR ORIGINAL IN FILM HAVING AT LEAST TWO SUPERIMPOSED SILVER HALIDE LAYERS; DEVELOPING THE EXPOSED PORTIONS IN BLACK AND WHITE DEVELOPER; REVERSAL DEVELOPING THE RESIDUAL RECORDS IN COLOR FORMING DEVELOPER, THEREBY PRODUCING NEGATIVE COMPARATIVELY COARSE GRAIN SILVER RECORDS AND POSITIVE RECORDS CO-EXTENSIVE WITH THE COLOR DEVELOPED RECORDS, OF COMPARATIVELY FINER GRAIN, AND SUSCEPTIBLE TO REMOVAL BY A SEELCTIVE BLEACHING AGENT WHICH HAS LESS EFFECT ON SAID COARSE GRAIN RECORDS THAN ON SAID FINE GRAIN RECORDS; REMOVING SUBSTANTIALLY THE ENTIRE SILVER IN ONE OF SAID LAYERS; AND TREATING THE OTHER LAYER WITH SAID SELECTIVE BLEACHING AGENT FOR A TIME SUFFICIENT TO REMOVE A SUBSTANTIAL PORTION OF THE SILVER OF SAID FINE GRAIN POSITIVE RECORD BUT TO LEAVE A CORRECTIVE SILVER MASK CONSISTING PREDOMINANTLY OF COARSER GRAIN AND BEING OF LOWER GAMMA THAN SAID COLOR DEVELOPED RECORDS. 